The invention relates to the field of turbines and, in particular, to the application of microturbines for electrical power generation.
Microturbines are small gas turbines typically used for on-site power generation. They are generally applied as back-up or auxiliary power sources for office buildings, retail stores, small manufacturing plants, homes and many other commercial facilities. These facilities have traditionally been powered by electric utilities via a grid of power distribution lines. Using microturbines, these facilities generate electrical power at their own sites, and avoid being solely dependent on conventional electrical power grids and utilities. Microturbines may also generate power at less cost and/or more reliably than the electrical power provided over the grid by electrical power utilities.
Microturbines are not self-starting devices. They require a starter and a power source for the starter. The starter usually includes a powerful electric motor and a battery which acts as the power source for the starter. If the battery loses its charge or otherwise fails, the microturbine cannot be started. Batteries fail due to a variety of causes, including being discharged if used too often to start the microturbine without being charged, if left uncharged and unused for an extended period of time (such as when the microturbine is not used for many months), or if a cell in the battery shorts out or otherwise fails. Accordingly, there is a need for an alternative power source to start a microturbine.
To safeguard against battery failure it has been proposed that the starter for a microturbine have an alternative source of power. Such an alternative power source may be the power grid provided by electrical utilities, as is disclosed in U.S. Pat. No. 6,031,294 ('294 Patent). However, the power circuitry that is disclosed in the '294 Patent for directing power from a grid includes an additional rectifier and contactor which are used exclusively to couple a power grid to start a microturbine. This additional circuitry needed to start the microturbine is expensive and complex. There is a need for power circuitry that may apply AC (alternating current) power and/or DC (direct current) power from a battery, power grid or other power source to start a microturbine that is not exclusively dedicated to starting, is not excessively expensive and is not complex.